Method of achieving controlled, variable ballistic dispersion in automatic weapons

ABSTRACT

A method of achieving controlled, variable ballistic dispersion in an automatic weapon is disclosed includes providing a plurality of cartridges, where each cartridge has a case and a projectile partially inserted into a mouth of the case forming a circumferential joint between the projectile and the mouth of the cartridge and held therein at a different pull strength. The method also includes providing a plurality of adhesive sealants, where each adhesive sealant of the plurality of adhesive sealants sets a design bullet pull strength that is different from each other adhesive sealant.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/748,853, filed on Oct. 22, 2018, the contents of which are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to small arms ammunition, and more particularly, to a method of achieving controlled, variable ballistic dispersion in automatic weapons.

BACKGROUND OF THE INVENTION

In firearms, ballistic dispersion is the pattern of bullet strikes on the target which diverge from the point of aim due to a variety of factors. Some examples of factors that may cause dispersion include a worn or defective firearm, variations in ammunition components or velocity, and wind or atmospheric conditions which result in a spread of impacts in the vertical and horizontal orientations.

Historically, the goal of ammunition and firearm makers has been to decrease dispersion for greater accuracy in firearms. The primary mechanism available to ammunition makers to decrease dispersion is by controlling the shot start velocity of the bullets. When two otherwise identical bullets are fired from the same weapon, at the same target with the same aim point, under the same ambient conditions, but at different velocities, the slower projectile will strike the target at a lower point than the faster projectile. This is due to varying ballistic trajectories which initially coincide at close range and diverge to a greater degree as the distance to the target increases.

The two factors leading to a consistent shot start velocity are a consistent propellant charge and a consistent pull strength (the force required to remove the bullet from the case mouth). A higher propellant charge will generally result in a higher shot start velocity. Likewise, a higher pull strength will in a higher shot start velocity, as a higher pressure is able to build within the cartridge before the bullet is released from the case. Generally, consistent pull strengths are achieved through consistent case thicknesses, compositions, annealing levels and crimp strength.

A consistent shot start velocity is particularly critical in long range rifles, where the difference in ballistic trajectories resulting from different velocities will have the most impact upon the actual point of impact. Consequently, great pains are taken to ensure as uniform a possible propellant charge and pull strength in ammunition rounds used by snipers, competition shooters, and the like.

With automatic firearms, accuracy is generally less important as such weapons are often used produce a suppressive field of fire over a larger area rather to place rounds on a specific target. Users of these weapons are often trained to scan the weapon side-to-side during fire to enhance this effect. While the effectiveness of modern machine guns is unquestioned, further improvements are possible.

SUMMARY OF THE INVENTION

A method of achieving controlled, variable ballistic dispersion in an automatic weapon is disclosed. The method includes providing a plurality of cartridges, where each cartridge has a case and a projectile partially inserted into a mouth of the case forming a circumferential joint between the projectile and the mouth of the cartridge and held therein at a different pull strength. The method also includes providing a plurality of adhesive sealants, where each adhesive sealant of the plurality of adhesive sealants sets a design bullet pull strength that is different from each other adhesive sealant. The method also includes applying a different adhesive sealant to the circumferential joint of each of the plurality of cartridges, exposing the plurality of cartridges to UV radiation or other curing agent until the different adhesive sealants cure to develop the design bullet pull strength, and combining the plurality of cartridges having the different adhesive sealants in an ammunition belt to form a plurality of different velocities and trajectories of respective projectiles when fired in an automatic weapon.

In view of the foregoing, it is an object of the present invention to provide a method of achieving controlled, variable ballistic dispersion in automatic weapons. These and other objects, aspects and advantages of the present invention will be better appreciated in view of the drawings and following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is an exploded schematic view of a cartridge;

FIG. 1B is a schematic view of the cartridge of FIG. 1A with a projectile inserted into a case thereof;

FIG. 2 is a schematic view of a back end of the case of FIG. 1A taken in the direction of line 2-2;

FIG. 3 is a schematic view of applicators applying adhesive sealants in accordance with the invention;

FIG. 4 is a schematic view of a UV light curing the adhesive sealants shown in FIG. 3; and

FIG. 5 is a schematic view illustrating a range of dispersion of projectiles.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the summary of the invention, provided above, and in the descriptions of certain preferred embodiments of the invention, reference is made to particular features of the invention, for example, method steps. It is to be understood that the disclosure of the invention in this specification includes all possible combinations of such particular features, regardless of whether a combination is explicitly described. For instance, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally.

Referring initially to FIGS. 1A-1B and 2, a conventional cartridge 100 includes a projectile (i.e., a bullet) 102 held partially within a case 104 forming a circumferential joint 110 between the projectile and the mouth of the case 104. The case 104 contains a propellant for ejecting the bullet 102 from the case 104 when the cartridge 100 is fired. The cartridge 100 also includes a back end 106 (surrounded by a rim grippable by a firearm ejector mechanism) opposite the bullet 102. The rim 106 typically houses a primer cup 108 filled with primer which ignites when struck with a firing pin, and which in turn ignites the propellant.

Referring additionally to FIG. 3, an adhesive sealant 112, 115, 117, 119 is being applied to a plurality of cartridges 100A, 1006 on a first production line 120. The adhesive sealant 112, 115, 117, 119 is selected in order to set the bullet pull strength by bonding the projectile 102 to the case 104 in accordance with an aspect of the invention. The adhesive sealant 112, 115, 117, 119 is formulated to adhere to the case 104 and the projectile 102 with a defined shear strength along the circumferential joint 110. Thus, selecting a particular adhesive sealant 112, 115, 117, 119 determines the pull strength needed to separate the projectile 102 from the case 104.

In this example, a plurality of adhesive sealants are provided 112, 115, 117, 119 where each adhesive sealant of the plurality of adhesive sealants 112, 115, 117, 119 is formulated to have adhesive properties that will result in a design bullet pull strength that is different from that resulting from each other adhesive sealant. In a particular aspect of the invention, each of the adhesive sealants 112, 115, 117, 119 masks crimping variables, reducing their consequences and homogenizing the final bullet pull strength. The adhesive sealants 112, 115, 117, 119 accomplish this masking effect through even distribution around the joint 110 formed between the cartridge case mouth and base of the projectile 102. This even distribution, due to the low viscosity and wicking properties of the adhesive sealants 112, 115, 117, 119 results in the desired bullet pull strength from each of the adhesive sealants 112, 115, 117, 119 and a stable release and flight pattern for the bullets.

The plurality of adhesive sealants 112, 115, 117, 119 are used in order to achieve varying desired design bullet pull strengths in a group of cartridges. As illustrated in FIG. 3, the plurality of adhesive sealants are applied using applicators 114, 118 that include non-contact precision jet valves 113, 116. The jet valves 113, 116 apply the respective adhesive sealant 112, 115, 117, 119 to the cartridge case mouth 110 and bullet 102 at the circumferential joint 110 of each of the cartridges 100A, 100B. The plurality of adhesive sealants 112, 115, 117, 119 are specially formulated to exhibit very low viscosity and to wick around the cartridge case mouth along circumferential joint 110 resulting in a smooth, consistent distribution of the adhesive sealant 112, 115, 117, 119.

Accordingly, more than one variation of adhesive sealant can be applied from different dispensers 114, 118 or sealant reservoirs 112A, 115A, 117A, 119A, which alternate in the passing of completed cartridges to achieve different bullet pull strengths. By substituting this method of sealing for the existing process, the ability to environmentally seal and either increase or decrease bullet pull strength (i.e. neck tension) in any number of variations greater than one may be achieved on the same production line 120.

Referring now to FIG. 4, the adhesive sealant 112, 115, 117, 119 is then cured in place on cartridges 100A, 100B, 100C, 100D on a second production line 130 using a UV light 122 having an array of UV LED curing lights 123A, 123B, 123C, 123D, 123E. At the desired wavelength and intensity, the UV exposure needed is no more than a few seconds. Further subsurface curing occurs anaerobically. The particular adhesive sealant 112, 115, 117, 119 is exposed to UV radiation until the particular adhesive sealant cures to develop the design bullet pull strength. After UV radiation curing is completed, the cartridges 100A, 100B, 100C, 100D, can be handled, tested, packaged and shipped in minutes without ever leaving the assembly line. The present invention is not necessarily limited to UV curing. For instance, adhesives cured via visible light could be used.

In a particular aspect of the invention, the adhesive sealant 112, 115, 117, 119 may have a composition comprising polyglycol dimethacrylate of 30-60% by weight, polyglycol dioctanoate of 30-60% by weight, saccharin of 1-5% by weight, cumene hydroperoxide of 1-5% by weight, and a photoinitiator of 1-5% by weight.

The adhesive sealant 112, 115, 117, 119 contains no class 1 ozone depleting chemicals. Accordingly, an additional advantage of the adhesive sealant 112, 115, 117, 119 described herein is that it is 100% active with no solvents. This eliminates the toxic fumes and allows the adhesive sealant 112, 115, 117, 119 to be applied continuously creating efficiency gains over previous batch processing methods.

The adhesive sealant 112, 115, 117, 119 may maximize bullet pull strength at approximately 300 lbf. As bullet pull strength increases, so does the pressure inside the case 104 prior to the bullet 102 firing. Accordingly, the adhesive sealants 112, 115, 117, 119 may be formulated to achieve a desired range of bullet pull strengths. For example, the bullet pull strength range may be from 125 lbf to 300 lbf. It will be appreciated that the total pull strength is also a result of the bonded surface area in the circumferential joint. This is impacted by caliber and other dimensional factors.

Referring additionally to FIG. 5, increasing or decreasing bullet pull strength has been shown to increase or decrease velocity of the projectile significantly without propellant loading variations. FIG. 5 illustrates the relationship between velocity and varying impact on the target. The same angle of firing with bullets launched at different velocities results in higher or lower impacts on the target. For example, a shooter 200 is aiming an automatic weapon 202 at the same angle while firing rounds with each having a different adhesive sealant with different bullet pull strength. As a result the cone of dispersion 204 of the bullets strike the ground at varying distances along different trajectories 206, 208, 210 and 212. Thus, the round having the highest bullet pull strength due to the adhesive sealant will have the highest velocity and the farthest trajectory 206. The round having the least bullet pull strength due to the adhesive sealant will have the lowest velocity and the least trajectory 212, and so forth.

In one aspect, application of an adhesive sealant with a higher bullet pull strength to a cartridge resulted in a gain of 130 feet per second over an unsealed cartridge and 102 feet per second gain over a lower strength sealant which itself exceeded the unsealed cartridge by 28 feet per second. With a base velocity of 2,575 for the unsealed cartridge, the low strength adhesive sealant velocity would be 2,603 and the high strength velocity at 2,705 feet per second.

According to ballistic tables for the .30 caliber 147 grain Full Metal Jacketed NATO projectile, applying low strength yields −12.86 Minute of Angle (MOA) of drop at 500 yards while higher strength results in −11.74 MOA of drop, which is a difference of 1.12 MOA or a 5.6″ difference through the adhesive sealant alone.

In a particular aspect, the cartridges 100A, 100B, are presented along a belt 120 which separates and aligns them. Instead of a single dispenser applying the same adhesive sealant, multiple dispensers 114, 118 apply different adhesive sealants 112, 115, 117, 119 from respective reservoirs 112A, 115A, 117A, 119A as determined by a computerized control system.

For example, since four rounds of non-tracing ammunition are later combined with a single tracing round in a pattern described as “4+1” and the tracing ammunition would typically be sealed separately in its own run, for example with a further differing strength, every group of four non-tracing cartridges would receive low 112, low to medium 115, medium to high 117 or high strength 119 adhesive sealant. When combined in the machine gun ammunition linking machine, each of the rounds would then have a different bullet pull strength and therefore a different point of bullet release pressure and velocity as described above, despite being otherwise identical (within manufacturing tolerances) with respect to caliber, construction and propellant load.

The ability of the present invention to achieve variable dispersion extends beyond the effect of different short start velocities on trajectory. For example, in practical use of a firearm including rounds with intentionally varied bullet strengths, there will be increased dispersion effects to recoil effects and cyclic rate variation.

In the case of the former, recoil in general causes the muzzle of the automatic weapon to rise against the vehicle mount or the shoulder of a ground user, so the lower the recoil impulse the closer the next round is generally to the point of aim. Recoil begins on the bolt face as soon as the primer is impacted. When also considering the response of the weapon to different recoil impulses, it will be appreciated that the higher shot start pressures will add more significantly to the height of the impacts while the lower pressure impacts should be close to the point of aim or lower. For example, a weapon firing for one second at high recoil levels would spread ten rounds wider in impact area on the target than the same weapon firing a lower recoil round. Without as much muzzle rise, the lower pressure ammunition would be expected to have lower dispersion in automatic fire. The present invention, by including a mix of both, can further achieve controlled dispersion by taking into these recoil effects.

In the case of the latter, it is believed that the “dwell time” between rounds is affected by increases or decreases in shot start pressures in gas and recoil operated weapons. The use of adhesive sealant, as described herein, to control the shot start pressure is will consequently further increase dispersion due to variable response of the weapon to the prior round's gas pressure level. For example, a weapon loaded with all low strength sealants would be expected to operate at a lower cyclic rate than those loaded with high strength sealant due to higher pressures generated internally from more complete propellant burn. A mixed belt of ammunition would then be expected to operate at a variable cyclic rate from round to round, amplifying the effect of shot pressures alone on ballistic dispersion.

In general, the foregoing description is provided for exemplary and illustrative purposes; the present invention is not necessarily limited thereto. Rather, those skilled in the art will appreciate that additional modifications, as well as adaptations for particular circumstances, will fall within the scope of the invention as herein shown and described and of the claims appended hereto. 

What is claimed is:
 1. A method of achieving variable ballistic dispersion from an automatic weapon, the method comprising: assembling a plurality of ammunition cartridges such that each of the plurality of ammunition cartridges has a different respective predetermined pull strength; packaging the plurality of ammunition cartridges into a group for firing sequentially from an automatic weapon.
 2. The method of claim 1, wherein assembling the plurality of ammunition cartridges includes applying a respective adhesive sealant to each of the plurality of ammunition cartridges in a respective circumferential joint between a respective case mouth and a respective projectile thereof, the respective adhesive sealants being formulated with different adhesive properties so as to achieve the different respective predetermined pull strengths.
 3. The method of claim 2, wherein applying the respective adhesive sealant to each of the plurality of ammunition cartridges includes injecting the respective adhesive sealant into the respective circumferential joint with an applicator having a non-contact jet valve.
 4. The method of claim 3, wherein each of the respective adhesive sealants is formulated to wick around the respective circumferential joint upon injection.
 5. The method of claim 2, wherein applying the respective adhesive sealant to each of the plurality of ammunition cartridges includes passing each of the plurality of ammunition cartridges down a common production line and applying each of the respective adhesive sealants from a respective applicator.
 6. The method of claim 5, wherein each of the respective applicators uses a non-contact jet valve to inject the respective adhesive sealant into the respective circumferential joint.
 7. The method of claim 2, wherein assembling the plurality of ammunition cartridges further includes at least partially curing each of the respective adhesive sealants using ultraviolet (UV) radiation.
 8. The method of claim 1, wherein each of the different respective predetermined pull strengths is at least 125 pounds force (lbf).
 9. The method of claim 8, wherein the different respective pull strengths vary from 125 lbf to 300 lbf.
 10. The method of claim 1, wherein the plurality of ammunition cartridges include at least three ammunition cartridges having the different respective predetermined pull strengths.
 11. The method of claim 10, wherein the plurality of ammunition cartridges include four ammunition cartridges having the different respective predetermined pull strengths.
 12. A method of achieving variable ballistic dispersion from an automatic weapon, the method comprising: passing a plurality of ammunition cartridges along a production line with at least first and second portions of the plurality of ammunition cartridges having respective adhesive sealants applied to respective circumferential joints between respective case mouths and respective projectiles thereof; wherein the respective adhesive sealants are formulated with different adhesive properties such that the first and second portions of the plurality of ammunition cartridges will have different respective predetermined pull strengths.
 13. The method of claim 12, wherein each of the respective adhesive sealants is applied from a different applicator.
 14. The method of claim 12, wherein each of the respective adhesive sealants is applied from at least one applicator having a non-contact jet valve.
 15. The method of claim 14, wherein each of the respective adhesive sealants is formulated to wick around the respective circumferential joints upon injection.
 16. The method of claim 12, further comprising passing the plurality of ammunition cartridges past at least one ultraviolet (UV) light and at least partially curing each of the respective adhesive sealants using UV radiation.
 17. The method of claim 12, further comprising packaging the plurality of ammunition cartridges into a group for firing sequentially from an automatic weapon with ammunition cartridges from the first and second portions being interspersed.
 18. A group of ammunition cartridges arranged for firing sequentially from an automatic weapon, the group comprising: a first ammunition cartridge having a first predetermined pull strength of a first circumferential joint between a first case mouth and a first projectile; and a second ammunition cartridge having a second predetermined pull strength of a second circumferential joint between a second case mouth and a second projectile, the first and second predetermined pull strengths being different.
 19. The group of claim 18, wherein the first and second predetermined pull strengths are determined by first and second adhesive sealants located, respectively, in first and second circumferential joints.
 20. The group of claim 18, further comprising a third ammunition cartridge having a third predetermined pull strength of a third circumferential joint between a third case mouth and a third projectile, the third predetermined pull strength being different from both the first and second predetermined pull strengths. 